This invention relates in general to a Micro Electro Mechanical Systems (MEMS) die. In particular, this invention relates to an improved method for controlling solder flow and surface tension when attaching the MEMS die to a surface such that the MEMS die will self-align to a desired position relative to the surface while the attachment solder is molten.
A MEMS die must typically be geometrically aligned with a mounting surface for optimal wire bonding. Typically, MEMS die alignment is a function of solder flow and solder surface tension. Non-uniform solder flow and insufficient solder surface tension however, is known to cause undesirable misalignment of solder-attached MEMS dies.
According to a known method, a round solder preform is placed onto a round pedestal of a mounting body and a rectangular MEMS die is placed onto the round solder preform. Often, the MEMS die is aligned to a desired position on the pedestal by an assembler who visually positions and hand-places the MEMS die without the aid of alignment tools. According to this known method, the surface tension of the molten solder may be insufficient to maintain a desired rotational alignment of the MEMS die relative to the pedestal. Thus, it would be desirable to provide an improved method for controlling solder flow and surface tension during MEMS die attachment such that the MEMS die will self-align to a desired position relative to a surface of a mounting body while the attachment solder is molten.